Knowing Your Own Strength with Conditional Injury in GURPS

So that’s what he’s been doing.

You caught me fair and square. This month, I’ve spent over a week trying to figure out how to best merge Knowing Your Own Strength (KYOS) with Conditional Injury (CI). The funniest part of the story is that this came from me trying to fit some new decapitation rules into GURPS because I don’t like the idea of, if you get killed by a blow to the neck, that’s decapitation. Then, I got to thinking that using damage multipliers with Knowing Your Own Strength is a tad weird because it’s based on logarithmic ST (though, maybe not logarithmic damage), so I was wondering if damage multipliers should just be damage bonuses.

Then, I found Anthony’s Logarithmic Damage. One way or another, that pointed me toward Conditional Injury. So, then, I wanted to marry KYOS with CI.

So, I started a thread about it. So far, I’m left with this:

Ultimately, what I want is a system to use Knowing Your Own Strength (KYOS) from Pyramid #3/83: Alternate GURPS IV and Conditional Injury (CI) from Pyramid #3/120: Alternate GURPS V. Ideally, it would be realistic, easy-to-use, and work directly with KYOS and CI as opposed to creating a parallel system. There has been a lot of great work so far, and I’m extremely grateful to each of the contributors.

THE +30 = ×10 SYSTEM

This is what Anthony’s Know Your Own Damage is based on, and Anthony has listed the advantages of this system here. It is complete, but it doesn’t satisfy the idea of directly working with KYOS and CI because there isn’t enough information on how the systems interact.

THE +24 = ×10 SYSTEM

This assumes that BL in KYOS is converted to be +10 = ×12. It’d be a bit of extra work. Plus, dataweaver mentioned that it “gives you easy squares and cubes”. Anthony argues that it gives “nasty numbers”, and dataweaver argues that it’s “less of a concern […] since we’re actually more interested in ranges of values than exact values”. Earlier in the thread, dataweaver detailed these values here.

THE +20 = ×10 SYSTEM

The +20 = ×10 system feels the best to me. It seems like it would take the least effort to get working directly with KYOS, especially because BL in KYOS is based off of +10 = ×10. KYOS also converts BS ST into KYOS strength this way since KYOS ST is based on 20 times the log of BS ST. dataweaver details a conversion from BS HP/damage to the +20 = ×10 system here. RyanW’s System is described by RyanW as being based on +20 = ×10 here.

RyanW’s System

  • RyanW’s original thread can be found here.
  • RT = (ST – 10) / 3 + 4.
  • WP = (ST – 10) / 3. Roll 1d6—on 1 or 2, give -1 WP; on 3 or 4, give +0 WP; on 5 or 6, give +1 WP.
  • Swing = +1 WP (or +3 ST).
  • BS ST-based weapon damage is divided by 2 and rounded away from 0, then applied to WP.
  • BS DR is converted to DR the same way BS HP is converted to RT.
  • When WP exceeds DR by 3 or less, the WP is reduced:
    • By 1: -3 WP
    • By 2: -2 WP
    • By 3: -1 WP
    • By 4+: -0 WP
    • Where multiple sources of DR apply, apply the reduction for each in turn and check the remaining against the next source of DR (which might be cumbersome in games where layered armor is common).
  • Apply the rules from CI normally starting at Injury and Severity.
  • ST [5/level], RT/WP [10/level], but you must stay in your allowable range.

My Suggestion

In order to keep the regular ST [10/level], I suggest multiplying everything before Severity by 3 and then dividing it by 3 for Severity, which also helps with the resolution.

  • RT = ST + 2.
  • WP = ST – 10. Roll 1d6–3, then apply result to WP.
  • Swing = +3 WP.
  • BS ST-based weapon damage is multiplied by 1.5 and rounded away from 0, then applied to WP.
  • When WP exceeds DR by 25 or less, the WP is reduced:
    • By 1: -19 WP
    • By 2: -14 WP
    • By 3: -11 WP
    • By 4: -9 WP
    • By 5: -7 WP
    • By 6: -6 WP
    • By 7: -5 WP
    • By 8–9: -4 WP
    • By 10–12: -3 WP
    • By 13–15: -2 WP
    • By 16–25: -1 WP
    • By 26+: -0 WP
    • Where multiple sources of DR apply, apply the reduction for each in turn and check the remaining against the next source of DR.
  • Severity = (WP – RT) / 3.

What I Don’t Know

  • Where RyanW’s system falls on the scale of realism.

dataweaver’s +20 = ×10 System

  • HP is based on +20 = ×10 (the big difference from Anthony).
  • RT = HP + 10 or 20 × log(BS HP).
  • WP = damage + 10.
  • BS DR is converted the same way that BS HP is, so BS DR 1 → DR 0 and BS DR 10 → DR 20 (and BS DR 0 → DR -∞).
  • To apply DR, use WP – DR to find out by how much to reduce WP.
    • ≤0: no damage
    • 1: -21 WP
    • 2: -13 WP
    • 3: -10 WP
    • 4: -8 WP
    • 5: -7 WP
    • 6: -6 WP
    • 7: -5 WP
    • 8: -4 WP
    • 9–10: -3 WP
    • 11–13: -2 WP
    • 14–19: -1 WP
    • ≥20: -0 WP
  • For damage, roll 5d, add the highest three dice to WP, then subtract 14 from the result to get the final WP.
  • The Conditional Effect Table for CI is rescaled so that the Severity column is divided by 3 and multiplied by 10. So, ±6 becomes ±20, ±5 becomes ±16, ±4 becomes ±13, ±3 becomes ±10, ±2 becomes ±6, and ±1 becomes ±3. All of the Severity modifiers need to be rescaled in the same way—e.g., impaling damage goes from +2 to +6.

What I Don’t Know

  • How to calculate HP (from ST, from weight).
  • How to add or subtract ST-based weapon damage.

Anthony’s +20 = ×10 System

  • HP is based on +30 = ×10 (the big difference from dataweaver).
  • RT = ST × 0.2 + 2.
  • ST = Mass × 2/3 – 2. However, if HP is based on Mass and damage is based on ST, the two values don’t align. To resolve this, add in weapon weight. Damage scales with ST + (weapon Mass/3).
  • Mass = (ST required to lift an object as 1 × BL).
  • RT = (Mass × 2/3 + 2) × 2/3 – 2.
  • 0.2 RT [2/level].

What I Don’t Know

  • How to add or subtract ST-based weapon damage. This seems to do with “Damage scales with ST + (weapon Mass/3)”.
  • How to calculate WP (from damage). This seems to do with “Damage scales with ST + (weapon Mass/3)”.
  • How to calculate DR.
  • How to apply DR.
  • How to rescale Severity and Severity modifiers.
  • In BS, a 125,000 lb creature is assigned BL 2,000. With KYOS, a 125,000 lb creature would be assigned BL 20,000. Why? Yes, KYOS gives ST = 10 × log(weight in lb/6). How realistic is each number?

A MESSY SOLUTION

Everything is calculated per BS except for ST, which is the default assumption of KYOS. However, for this, damage is reverted to how it was before for calculating reasonable WP.

  • ST 10 [0] = BL 20 = 1d-2/1d damage = HP 10 [0] = 125 lb.
  • ST 16 [60] = BL 80 = 2d-1/3d+2 damage = HP 20 [8] = 1000 lb.
  • ST 20 [100] = BL 200 = 3d+1/6d-1 damage = HP 32 [24] = 4096 lb.
  • All of this is input in CI as normal.

The only thing that doesn’t work is KYOS ST = 10 × log(weight in lb/6) with -4 for humans. That would give ST 9, ST 18, and ST 24, respectively. It just doesn’t seem to line up with BS HP = 2 × (weight in lb)^(1/3), assuming ST = HP, then converting BS ST to KYOS ST.

And it is messy. It requires buying extra HP, and damage will always be looked up from a table because the progression is awkward. Plus, this relies on the large HP and damage bands in CI.

Though, I don’t like the damage progression in BS. So, I use tbone’s New Damage for ST. If you don’t mind everything being a bit deadlier, use it as is with “medium” damage and “large” damage on the New Damage Table (or you can use it in conjunction with tbone’s Toughness). Otherwise, per tbone’s suggestion, you can use “small” damage and “medium” damage on the Expanded New Damage Table (and it’s suggested to give big weapons a damage boost). Personally, I think there’s a nice middle ground in using the New Damage Table and shifting the table to ST 7 is ST 10, so ST 10 is 1d-2/1d damage.

That leaves me with the following:

  • ST 10 [0] = BL 20 = 1d-2/1d damage = HP 10 [0] = 125 lb.
  • ST 16 [60] = BL 80 = 2d/3d damage = HP 20 [8] = 1000 lb.
  • ST 20 [100] = BL 200 = 3d/5d-1 damage = HP 32 [24] = 4096 lb.

Alternatively, you could throw out KYOS altogether and use tbone’s A Better Cost for ST and HP. Compared to KYOS, 300 points for tbone’s BS ST 100 (BL 2000, 10d/15d damage) is still more expensive than 200 points for KYOS ST 30 (BL 2000, 5d+2/6d damage), but it’s not horrible.

  • ST 10 [0] = BL 20 = 1d-2/1d damage = HP 10 [0] = 125 lb.
  • ST 20 [100] = BL 80 = 2d/3d damage = HP 20 [0] = 1000 lb.
  • ST 32 [155] = BL 205 = 3d/5d-1 damage = HP 32 [0] = 4096 lb.

Current Thoughts

It really is a toss-up between a few options right now.